1. Field of the Invention
This invention relates to a solar charger that charges a rechargeable battery via a solar cell, and in particular relates to a solar charger that can efficiently charge a rechargeable battery over the four seasons of the year.
2. Description of the Related Art
Solar cells produce electricity most efficiently when oriented perpendicular to the sun's rays. This is because solar energy is most efficiently transferred to solar cells irradiated in this orientation. The sun's rays irradiate solar cells with energy of approximately 1 KW per square meter. Consequently, solar cells with an energy conversion efficiency of 10% generate 100 W of electricity per square meter. However, if the solar cells are inclined at an angle of 45° with respect to the sun's rays, solar energy supplied to the solar cells drops by 30%. If the solar cells are further inclined to an angle of 60°, solar energy supplied to the solar cells drops to one half. This shows how important orienting solar cells perpendicular the sun's rays is for efficiently charging rechargeable batteries via solar cells.
To efficiently charge rechargeable batteries via solar cells, the present applicant developed a solar charger that can change the angle of inclination of the solar cells (refer to Japanese Patent Application Disclosure SHO 63-19770[1988]).